A video conferencing system includes a plurality of device-specific transceivers that are interconnected by telecommunication lines. The basic components of a transceiver include a processing unit or set box, one or more video input/output devices, and one or more audio input/output devices. For example, the transceiver may be a personal computer having a video conferencing interface board for controlling a video camera, a video screen, an audio microphone and an audio speaker. The interface board captures and digitizes frames of analog video input received from the camera and generates an analog video output for driving images on the screen. In addition, the interface board receives analog audio input from the microphone and sends analog audio output to the speaker.
In addition, each transceiver includes a communications link to one or more other transceivers, such as a LAN controller, an ISDN controller or a telephone modem. Video conferencing systems are capable of performing video conferencing between two or more transceivers so long as the video and audio information communicated between the transceivers are based on the same communication format or protocol. Therefore, when a local transceiver utilizing a particular video and audio format wishes to video conference with a remote transceiver exhibiting a different format, a telecommunications interface unit must be situated between the transceivers to convert the local transceiver's format to the remote transceiver's format. Specifically, the telecommunications interface unit receives telecommunication signals in the first video and audio format, converts the signals to the second video and audio format, and transmits the converted signals to the remote transceiver.
Video conferencing systems for communicating video information from one transceiver to another are generally known. Examples of such systems are described in U.S. Pat. No. 3,618,035 to R. L. Simms, Jr., which issued on Nov. 2, 1971; U.S. Pat. No. 4,995,071 to J. Weber, et al., which issued on Feb. 19, 1991; U.S. Pat. No. 5,315,633 to J. J. Champa, which issued on May 24, 1994; U.S. Pat. No. 5,375,068 to R. S. Palmer, et al., which issued on Dec. 20, 1994; and U.S. Pat. No. 5,438,357 to S. H. McNelley, which issued on Aug. 1, 1995. However, the above patents do not describe any type of telecommunications interface unit for converting a video and audio format used by one transceiver to a different video and audio format used by another transceiver.
Outside of the realm of video conferencing systems, devices for converting video signals from one format or protocol to another are well known. For example, U.S. Pat. No. 5,453,792 to Gifford et al, which issued on Sep. 26, 1995, provides a system for enabling a special effects module, which operates at one frame rate, to be interconnected into a network utilizing a second frame rate. In particular, television signals formatted in a PAL form are converted to a frame rate of 30 frames per second and, then, are applied to the special effects module. After being processed by the module, the resulting signals are reconverted back to the original frame rate and input format for transmission purposes. The system performs the intermediate conversion so that processing can occur in the context of the converted format. Another example of a video conversion device is described in U.S. Pat. No. 5,497,373 to J. S. Hulen, et al., which issued on Mar. 5, 1996. This patent illustrates a multimedia interface with plural digital signal processors ("DSPs"), each one dedicated to conversion of one format into a second signal format. Under control of a host messaging center which receives an indication of the input protocol, a dedicated DSP is selected to perform the conversion.
However, existing video conversion devices do not address the complexity and unique difficulties that are encountered by video conferencing systems. In order to perform video conversion, a telecommunications interface unit must know the exact video and audio formats or protocols of all transceivers that communicate through the unit. This task would be particularly difficult for a telecommunications interface unit that services a large commercial market since such markets have a wide variety of different transceivers that use different communication formats. In addition, the telecommunications interface unit must have a specific conversion unit or routine for every combination of conversions that is possible for these video and audio formats. Accordingly, not only are conventional telecommunications interface units costly to manufacture and maintain, but it is also difficult to keep such units up-to-date as video and audio formats change and/or increase in number. Further, advanced service features, such as dynamic multipoint conferencing, broadcasting, multicasting, global directories, private user groups, video on demand, video mail and security, are difficult and expensive to implement since each feature must be specifically configured for each video and audio format.